Certain food which is to be cooked is cooked in steam-pressure cooking utensils under an excess pressure inside of the steam-pressure cooking utensil, so that the steam-pressure cooking utensil must be provided with a safety valve which, at a specific excess pressure, vents steam and thus lowers the pressure in the cooking utensil.
It is known to combine the safety valve with a cooking valve, wherein the spring tension which presses the valve against its valve seat can be varied to adjust for the different cooking stages. This valve thus works as a regulating valve and keeps the pressure in the cooking utensil at a predetermined value. It is furthermore known to also provide such a cooking and safety valve with a cooking indicator, namely a piston which is lifted against a spring force in dependence on the pressure in the steam-pressure cooking utensil and which thus indicates with its markings the level of the pressure in the steam-pressure cooking utensil.
Such a steam-pressure cooking utensil is operated at a high pressure, which means that care must be taken that the steam-pressure cooking utensil cannot be opened under pressure. This safety measure also serves to prevent pressure from building up in the steam-pressure cooking utensil when the lid and utensil are not correctly closed. As a safety measure, a locking pin is provided which can be moved into the bayonet lock of the lid and utensil, so that in this position relative rotation of the lid and utensil is no longer possible.
It is known from German Offenlegungsschrift No. 17 79 501 to extend the control button for the adjustment of the initial tension for the safety and cooking valve and thus for the individual cooking stages, and to let the extended end, during its turning movement into the cooking stage, cooperate with a locking pin which is moved downwardly against a spring force and thus causes a locking or rather a release of the utensil and lid. We are dealing here with a one-button automatic, in which only in the ventilation position of the safety valve can the locking pin permit opening through rotation of the lid on the utensil. This also assures that the safety valve can only be closed when the steam-pressure cooking utensil was properly closed with its bayonet lock, namely when the recess in the utensil edge for receiving the locking pin lies exactly under the pin. This known solution thus offers safety features against an unintended opening and closing of the steam-pressure cooking utensil, but this one-button automatic is also very complicated and thus, on one hand, expensive to manufacture and, on the other hand, susceptible to breakdown during operation, so that breakdowns in operation must be expected in the long run.
A basic purpose of the invention is to suggest a steam-pressure cooking utensil of the above-mentioned type which has a cooking and safety valve and a locking mechanism in which the steam removal and unlocking or the closing of the cooking and safety vavle and the locking is done with an operating button, wherein it is assured that no residual pressure can remain in the utensil, and which is basically simple in design and thus inexpensive to manufacture and also is reliable in operation in the long run. A further purpose involves permitting removal of the safety valve only after the lid has been removed from the utensil.